A head-up display device is known as an information display device for the automobile and the like.
PTL 1 discloses a head-up display device that, using a concave mirror as a turning mirror, can be change a position of a virtual image by changing a distance between a display that is an object point and the concave mirror within a range where a virtual image point of the concave mirror appears in a manual or automatic manner or by a combination thereof.
PTL 2 discloses a vehicle head-up display device including a light source, a scanning unit that forms light from the light source into two-dimensional shape, a screen that forms an image of the scanning light, and a projection unit that projects a picture on the screen. In the vehicle head-up display device, a position of the projected virtual image can be changed by changing a distance between the projection unit and the screen.